• Chemical Bond: a force that holds atoms or ions together as a unit.
– Bonding takes place when atoms are unstable and willing to react.

• The stability of an atom is dependant on the atoms electron configuration and the number of valence electrons.
• Valence Electron - an electron in the outer most energy level.

• The number of an elements valence electrons corresponds to family number of the Group A elements.
• Valence Electron diagrams are generally represented by electron dot diagrams that shows an atoms correct number valence electrons.

• When an atom has a "full valence shell" which is 8 electrons, it is considered unreactive and will not bond.
• Which family on the periodic table is represented by these atoms?

• All other atoms on the periodic table are trying to become stable by gaining, losing or sharing electrons to acquire a full outer valence of 8 electrons.
• The different types of ways that atoms gain this full outer valence is how we classify the different types of bonds. In this course we will be studying ionic and covalent bonds

• Some atoms tend to donate or accept electrons to gain a full outer valence.

• Metals like Sodium and Magnesium will lose electrons to become a positively charged cations.
– Left side of the perioidic table.
• Non-Metals like Oxygen and Fluorine will gain electrons to become negatively charged anions.
– Right side of the periodic table.

Ca
K
Br
Element Electrons
Gain or
Lost
Ion Created Cation or
Anion?
S

• Ionic Bonding is a type of chemical bond that occurs when a positive cation and a negative anion attract to one another.
– Remember: Opposite charges attract!
• To write the chemical formula for an ionic bond, the charges of the cation and anion must be balanced with subscripts to allow for an overall charge of 0.
– Subscript - a number used to show the relative numbers of atoms of the elements present in a chemical formula.

Cation
Mg +2
Anion
O -2
Chemical Formula
Mg +2
Na +1
Cl -1
O -2

• An ionic compounds chemical formula tells the ratio of cations to anions but it doesn't exactly explain how the ions are arranged.
• Ions are held in place by their charges in repeating patterns known as lattices.
• Solids that have ions arranged in these structures are known as crystals.
– Crystals can be cubic, hexagonal, and other shapes depending on the arrangement of ions.

• Many of ionic compounds properties come from the strong attractions of ions in crystal lattice structures.
High Melting Point
Good conductor in solution or when melted
Tend to Shatter or Cleave

• I
• P
• Cs
• Al

• Cation Anion Formula